Learn a Linux command every day (24): chattr / Lsattr

Brother of migrant workers 2021-01-21 19:56:33
learn linux command day chattr

chattr Used to change files ( Expand ) attribute . Usually we call this property a special property .

lsattr View file extension properties .

This special property has the following 8 Patterns :

a # The qualification file has some function . This is very useful for log files , such as , Deletion is not allowed , Only content can be added to it .
b # Do not update or modify the last storage time of a file or directory
c # Compress a file or directory and store it
d # Exclude files or directories from the dump operation
i # Lock file or directory , Not changed
s # Secretly delete files or directories
S # Dynamically update files or directories in real time
u # Prevent files or directories from being accidentally deleted 

If the file or directory is configured with the above 8 One of the extended properties , adopt lsattr The command can see :

[root@centos7 testdir]# lsattr
----i----------- ./dir
# The result shows that the directory is configured with extended properties
[root@centos7 testdir]# chattr -i dir
[root@centos7 testdir]# lsattr
---------------- ./dir

Grammar format

chattr [ Options ] mode file
lsattr [ Options ] file

Option description

chattr Option description

-R # Recursive processing , Add this extended attribute to all files and subdirectories in the directory
-v< Version number > # Set the file or directory version number
-V # Display during execution of instructions ;
+ < attribute > # Add an extended property of a file or directory
- < attribute > # Release an extended attribute of a file or directory
= < attribute > # Specify an extensibility to a specified file or directory 

lsattr Option description

-E # Displays the current value of the property
-D # Displays the name of the extended property
-R # recursive
-V # Display version information
-a # List all files in the directory , Including hidden files
# Be careful -E -D -R The three options can't be used together , They are mutually exclusive .

Application, for example,

# The function of preventing false deletion
[root@centos7 testdir]# chattr +a test2.txt
[root@centos7 testdir]# lsattr test2.txt
-----a---------- test2.txt
# Direct substitution is not allowed , Only additional content is allowed
[root@centos7 testdir]# echo "12345">test2.txt
-bash: test2.txt: Operation not permitted
# See if the file or directory has extended properties
[root@centos7 testdir]# echo "12345">>test2.txt
[root@centos7 testdir]# lsattr
---------------- ./dir
---------------- ./test2.txt~
-----a---------- ./test2.txt
lsattr: Operation not supported While reading flags on ./cp

These two commands are also commonly used in daily work , Lock file , Or when a file or system fails, it can be used for troubleshooting .

[root@centos7 testdir]# lsattr
---------------- ./dir
---------------- ./test2.txt~
----i----------- ./test2.txt
lsattr: Operation not supported While reading flags on ./cp
[root@centos7 testdir]# echo "12345">>test2.txt
-bash: test2.txt: Permission denied

For example, the above situation , If this file is a file to store data in real time , locked , Then it may cause application running failure , therefore , Now you can go through lsattr Command to view and check .

This article is from WeChat official account. - The road of technology for migrant workers (jishuroad)

The source and reprint of the original text are detailed in the text , If there is any infringement , Please contact the yunjia_community@tencent.com Delete .

Original publication time : 2021-01-21

Participation of this paper Tencent cloud media sharing plan , You are welcome to join us , share .

本文为[Brother of migrant workers]所创,转载请带上原文链接,感谢

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